Living things breathe in oxygen from the air and exhale carbon dioxide from the lungs. Respiratory failure happens when the lungs cannot get enough oxygen to the blood or cannot exhale carbon dioxide properly. It is a serious medical emergency when a person cannot breathe independently and can be fatal if not managed on time. Any condition that affects the muscles, nerves, bones, and tissues that help breathe can lead to difficulty breathing. For example, pneumonia, COVID-19, cystic fibrosis, COPD, ALS, and spinal cord injury to the chest.